Doffer comb



July 29, 1952 E, w, SMITH 2,604,669

DQFF'ER COMB Filed 001;. 13, 1950 FEEQUEAKX INVENTOR. Edward W. SmIHxPatented July 29, 1 952 UNITED STATES PATENT OFFICE 2,604,669 I, g I f gDOFFER M Edward W. Smith, Melrose Highlands, Mass.

Application October 13,1950, Serial No.,190,003

12 Claims.

The present invention relates to dofier combs which are used in removingfibers from wire cylinders and other type cylinders of carding and othermachines.

In the preparation of many types of fibers for subsequent processinginto yarn, felt, etc., it is common practice to partially at least,align the fiber involved by passing them through a carding machine. Thevarious steps through which the fibers are passed need not be discussedhere since the operation is well known to those skilled in the art ofsuch fiber preparation. At the output end of the machine the more orless oriented fibers are picked up by a slowly revolving cylinder whosewire studded surface carries them in the form of a thin web from whichthe web is removed by the doifer comb.

In practice this comb consists of a metal strip with a serrated edgewhich is made to oscillate through a small angle tangent to the cylinderso that-inthe course of operation the web is removed continuously fromthe surfaceof the revolving cylinder. Furthermore in the course ofremoval a substantial amount of extraneous materialsuch as bits ofleaves etc., in the case of cotton, are dislodged from the web by theimpact of the comb in removing it from the cylinder. While it is currentpractice to apply the necessary torsional movement of the comb about theaxis on which it oscillates by means of an eccentric mechanism, thereare definite limitations to the speed at which the comb can be made tooscillate by this means because of its inertia which in turn, causesunnecessary wear and tear, difiiculties on the eccentric mechanism,lubrication difliculties and many other problems which are present athigher speeds of the usual mecha nism used. It is the purpose of thepresent invention to disclose a method and means whereby the necessarytorsional acceleration of the comb about its supporting axis can beaccomplished conveniently at much higher speeds than heretofore and atthe same time reduce or minimize the extra stresses which wouldotherwise be imposed upon the comb eccentric mechanism.

The present invention also provides a mechanism which will operate andstart with a minimum of power and will have its force and stressesbalanced so that there will be comparatively little Vibration outside ofthe Vibratory elements of the comb itself. g

The merits and advantages of the present invention will be more readilyunderstood from the specification below when taken in connection with,the drawings illustrating an embodiment thereof in which- Figures 1 and2 show diagrammatic illustrationsfor explaining the principles ofthepresent invention. 1

Figure 3 shows a longitudinal section through a dofr'er comb of thepresent invention.

operation of the present invention.

Figure 6 shows a section on the line '6-6 of Figure 3.

. or the like 2, having a torsional stiffness. 1 The other end of shaft2 is solidly secured to a solid Figure .7 shows. a section on the line7-1 of Figure 8 of a modification of a detail'of Figure .3, and

Figure 8 shows a section on the line 88 Figure 7. I

The principles of the present invention can best be understood byreference to Figure 1, where, in schematic form, is shown an inertiaelement I solidly secured to one end of a shaft body 3, large comparedto the inertia element 1. If now the inertia element l is rotatedslightly about its axis this action will result in torsion. beingapplied to shaft 2, and when the torque which brought aboutthe rotationof element I just referred to, is removed, element 1 willos iil- -g latetorsionally at a frequency which is deter-' mined by the magnitude ofits inertia and the torsional stiffness of shaft 2.

While such a system can be made to have any desired frequency andangular amplitude of vibration, it presupposes that the supporting bodyI 3 be large compared to the inertia element l which is not always easyto achieve. A' closer examination of the problem will indicate wh'atlsreally needed at the point where the body3 is secured to the shaft, isnot so much an infinite mass as it is a torque which is at alltimes'equal and opposite to the torque delivered to shaft 2 by theoscillation of. inertia I. If this could be achieved and applied to theend of the shaft secured to body'3, the purpose of body 3 would beachieved because at this point there would be no rotation of shaft 2 andthe need for alarge body 3 could be avoided.

The method by which the need for a more or less infinitely large mass towhich the end of shaft 2 is secured, can be avoided, is shownschematically in Figure 2. Here we have the same inertia element!secured to a shaft 2, butin this case shaft '2 is made longer and asecondinertia at the opposite I If now torque'is applied to inertiaelements I and 15m thedirec element I is solidly secured to it end frominertia element I.

tions indicated by the arrows, and then released, inertia element I willoscillate as before and inertia element I will also oscillate but in theopposite direction at all times. Thus at the nodal point 4 the forcesexerted on the shaft 2 will be equal and opposite with a resultantabsence of motion of the shaft at this point and, insofar as inertiaelement 1 is concerned, the effect of the solid member 3 is obtained butwithout the need of its size and mass.

It is, in effect, as if a mirror image of the inertia element l andshaft 2 had been introduced in place of member 3 and with the samephysical effect.

The means by which the above principle is applied to the high speedoperation of adoffer comb will now be described in connection. withFigures 3 and 4.

The comb 5 is carried on supporting arms 6 which,in turn, are solidlysecured to a tube 1. One end of the tube 1 is solidly secured to atorsion shaft 8 at the enlarged head 9, by welding, force fit, or othersuitable means; The other end of the tube 1 is free to turn on theenlarged end ll) of shaft 8. Furthermore an inertiaelement H is solidlysecured to this same end of the torsion shaft 8 as shown. In practice Iprefer to have the inertia element H so designed that it will have thesame inertia as the combined inertia of the comb 5, support arms 6, andthe tube 1 so that the nodal point or point" of zero angular rotation ofshaft 8 will occur at the center although this is not necessarilyessential as will presently appear.

Assuming that a frequency of oscillation has beenichosen and an angularamplitude of os cillation, the maximum torque required to give thenecessary acceleration to the inertia of the combination of comb 5,support arms 8 and. tube 1, can be determined from the relationshipTorque 12J1naw where Torque is the torque required in inch pounds Jill,is the mass moment of inertia in pound" feet squared of the above,combination, a is 21: times the frequency in cycles per second, anda isthe angular amplitude'of motion in radians.

In this connection it should be remembered that such a comb would.normally beoperated 3/ lGT' 15,0001r whered is the torsion shaftdiameter in inches, and,T the maximum torque required in inch po n Thelength of shaft required may be determinedfrom the relationship whereLis the active length of the torsion shaft 8 from the nodal point to thepoint where it is solidly secured to tube 1. above lpreferto maketheinertia of the counterbalancing inertia element l I, that of thetube-comb assembly,

Since as mentioned the same as this in effect means that the nodal pointwill be at the mid dle of torsion shaft 8 and L then becomes of thetotal length. d, in the above equation is the shaft diameter in inchesas determined above, 1 the required frequency of oscillation in cyclesper second, and J the moment of inertia of the comb-tube assembly on aweight basis, i. e. the sum of the weights of the various componentstimes the square of their distance from the axis of oscillation ininches.

Since the physical shape of the counterbalancing inertia can take manyforms, its construction will not be discussed here in detail except topoint out that its moment of inertia J, on a weight basis, should be thesame as the moment of inertia J which can be arrived at as indicatedabove.

It should also be kept in mind, that although mention has been made ofthe inertia of certain specific parts of the tube-comb assembly such asthe comb, support arms. and tube, the

inertia value used in computing the torque re quired and the torsionshaft length and diameter should include these elements plus any otherinertias connected to this assembly and oscillating with it which may beinvolved in the con-.- struction and operation of the assembly.

Inconsidering such a system as hasbeen described above it will be notedthat it is a mechanically resonant system and the torque required forits operation at frequencies both on and off resonance followsa curvesubstantially as shown in Figure 5. As will be noted from,

this curve the pulsating torque required to maintain the system inoscillation at frequenciesother than the resonant frequency is muchgreater than that required at resonance.

One of the purposes ofthe presentinventionisto provide a simple.andeffective mechanical means for bringing the oscillating system up tothe resonant frequency and thereafter supply ing it with such torque. asmay be .necessary to take .careof the load. The method and means. bywhich this isaccomplished can, best be; understood by reference toFigures 3 and 6.,

Referring now to Figure3, a casing 12 isprovided with an annular groove13 divided into two semi-circular compartments by the dividing.

members 14. A matching element l5 (Figure .3)

is provided with ears l6-whose inner and outer surfaces are curved andhave the same radiiof curvature respectively as the inner and outercurves of the annular groove iii in the casing I2. These ears areprovided with holes Hforming an interconnecting passage between the twoflat surfaces of the ears. If now memberli'is placed in position oncasing [2 with ears [Sprojecting into the two annular compartmentsformed in groove l3by. dividing member l4, element l5 may be rotatedthrough a substantial,

angle back and forth sincethe inner andouter curved surfaces of ears 16match snugly but,

without. undue friction, the inner and outer curved surfaces of the twochambers. It will alsobe noted that a cover plate [8 anda sealing ring,Hare providedto make the two chambers just mentioned, liquid tight. Anyleakage which,

might develop from the chambers to theback of element I5 is effectivelyprevented from ,egressby packing gland 20.

Now. if the unit is assembled with the two chambers completely filledwith a liqui d such.as

oil and an oscillating torque is applied toshaft 2 I, by any suitablemanner such as a crank shaft nomes and eccentric, there will be'apressure exerted on the ears I6 tending to rotate them slightly innecessarily be transmitted to casing l2 and shaft 22 joined to theenlarged head 9 at the end of the torsion shaft 8, and its magnitudewill'be pro-' portional to the size of the holes H and the viscosity ofthe oil being used. If the resistance offered to the rotation of shaft22 is slight the angular velocity of shaft 2| will be transmittedpractically undiminished to shaft 22, but if the resistance offered tothe rotation, or oscillation, of shaft 22 is great, then oil will beforced through the holes I! and a lesser velocity will'be transmitted toshaft 22.

The method by which this mechanism can be used to advantage in theoperation of the resonant doifer comb arrangement is shown in Figure 3and can best be understood from the following description.

As an example, let us suppose that shaft22 of the clutch mechanism shownin Figure 3 is energized by shaft 2| on the other end of the clutch andthat shaft 2| is connected to a motor driven eccentric to oscillateshaft 2| through some angle about its axis corresponding to the desiredangular amplitude of comb 5. In so doing comb assembly 5 will attempt tomove at the same fre-- quency and amplitude as shaft 2| is being driven,but by reference to Figure 5, it will be noted that the torque requiredto maintain a given angular amplitude at frequencies below the resonancepoint are very much greater than those required at resonance which isthe low point of the curve of Figure 5. Therefore if the clutch were notprovided the motor driving the eccentric connected to shaft 2| wouldhave to provide a torque many times larger to start the comb inoscillation at the given angular amplitude than would be required to runit at resonance.

The advantage in the use of the mechanism shown at the left end ofFigure 3 and in Figure 6, can therefore be appreciated. With theeccentric starting from a dead stop the torque required to maintain comb5 in oscillation at a given angular amplitude of resonance may begreater than the motor can conveniently supply. When this occurs thepressure exerted on the oil by ears 5- causes oil to be forced throughholes I! and element l5 slips with respect to casing [2 thus reducingthe angular motion of comb 5 and therefore reducing the torque requiredto oscillate it, and permits the motor to gain speed. As the motordriving the eccentric builds up in speed, so also does the comb and asthe speed approaches resonance the torque required to drive c0mb'5progressively reduces less and less, slip takes place between ears I6and casing |2 until finally, at the resonance point the slip issubstantially zero and the comb is being driven at the same angularamplitude as the eccentric.

By the above means the size of the motor required to start and run thecomb may be very much less than would otherwise be'the case.

The cross sectional area of the groove, the size of the hole in theears, and the viscosity of the oil used are a matter'of design. However,as an example I have found that using a groove inch square with the holein the ears 3% inch in diameter, and using oil of a viscosity of'20,000centistokes, 170 watts can be transmitted with no appreciable slip atspeeds in the neighborhood of 3600 vibrations per minute with an angularamplitude of the comb of .0803 radian corresponding to a stroke 015%inch at the comb oscillating about an axis 4 inches distant.

The amplitude of the comb throughout its length will be substantiallyuniform since the tube is sufficiently rigid so that it will not havetorsional displacement along its length'that the balanced shaft 8 willhave at the frequencies mentioned above.

Mention has been made above of the act that I prefer to design thecompensating inertia so that its inertia will equal the inertiaof thecombtube assembly and that under these circumstances the nodal point orpoint of zero angular displacement of the torsion shaft will occur inthe middle. While this is generally true and offers a solution of theproblem which is most economical of material the compensating inertianeed'not necessarily have the same inertia as the comb assembly. In factin certain special cases it may be desirable to have them unequal. As anexample it might happen that for the angular amplitude desired at thecomb the value of L as determined by the method described above might besuch that using a counter-balancing inertia of the same value as that ofthe comb assembly would mean that the length of the torsion shaft 8would be such that the combination would be too long for installation onthecard withwhich it was intended to work. This difficulty may beovercome by using a counterbalancing inertia larger than that of thecomb as will be understood from the following.

Earlier it was pointed out that the opposing torques at the nodal pointmust be equal and opposite. However, it will be noted from the equationdetermining the maximum accelerating torque required that this value isdirectly proportional to both the inertia and the maximum angularamplitude, for the same frequency. Therefore if the inertia of thecounterbalancing inertia is increased and its angular amplitude reducedin the same proportion, then the torque remains constant and thecriterion of equal and opposite torques at the nodal point is compliedwith. Under these circumstances it willalso beobvious from the above andfollowing equations that although the shaft diameter remains constantfor the same fiber stress, its length in the sofcase of the increasedvalue of inertia in the counterbalancin'g inertia is reduced, and in thesame proportion as the increase in the value of the inertia.

Thus, for instance, if the value of L for a given comb assembly,frequency, and angular amplitude, comes to 18 inches, and we use anequal inertia in the counterbalance, then its shaft length L will be thesame, making the overall length of the torsion shaft, 36 inches. If,however we design the counterbalance to have an inertia twice that ofthe comb assembly, it will oscillate at /2 the comb angular amplitudeand its shaft length will then be 9 inches instead or 18 inches makingthe overall length of the torsion shaft 27 inches instead of 36 inches.

While there is no sharply defined line of division in operating speeds,I prefer to use the mechanically driven eccentric and clutch arrangement for providing the pulsating torque required for oscillatingthe comb at the lower speeds, say up to 3600 vibrations per minute.-vFor speeds substantially above 3600 vibrations perminute, say 5000-7000per minute.

The driving arrangement which I prefer to use for speeds above 3600 perminute, although it can be used with equal effectiveness at speeds of3600 per minute or lower, is shown schematically in Figures? and 8,where respectively Figure '7 is a longitudinal section of the drivingassembly and Figure 8 is a sectional view of the driving system.

. Referring now to Figure'i, the comb-tubeassembly. is solidly securedto the further end (right end as viewed in Figure 3) of the. torsionshaft 8, in the drawing and the tube; 1' is free to move with respect tothe torsion shaft 8 at its end section 9' where because of its enlar edend it acts as a bearing to support the left end (as viewed in Figure 3)of the tube-comb assembly. The tube 1' at its end, designated as 24, hasa shoulder with an extending neck on which the armature 24' of a D. C.motor is mounted or formed and adapted to be rotated through at least asmall angle with respect to the field structure 25. This structure maybe made to supply the necessary pulsating torque required to energizethe-system by furnishing direct current to the field windings 26 andsupplying alternating current of the desired frequency of vibration ofthe comb, to the armature. However I prefer to connect the field andarmature windings in series and then supply alternating current ofone-half the desired frequency of vibration to the comb for reasonswhich will appear below.

First of all the use of such an arrangement eliminates the necessity fora sepa-. rate D. C. exciting current for the field winding since aseries connection of this sort would supply alternating current to bothfield and armature and results in pulses of torque being delivered bythe motorl Ihus if alternating current at a given instantis such to makethe two, poles north as indicated by N in Figure 8. and the remainingtwo south, then with the current in the turns on the armature directlyunder the north polesfiowing in a direction perpendicular to theendtoward theplane of the paper, the armature would tend to turn in adirection counter-clockwise with respect to the pole pieces. The samewould be true under the south poles because at the same instant both theflux in the south poles and the current in the windings under them wouldbe flowing in the opposite direction to the flu rin the north polesandthe current in the windings under them. r

This same condition would hold true when the direction of the flow ofalternating current reverses at the next half cycle; there will again bea tendency for the armature to rotate ina counterclockwise directionwith respect to the field. Thus since this condition occurstwice percycle of the alternating current there willbe two torque pulsations ofthe armature. per cycle of alternating current with respect to thefield,

It will also be notedfrom Figure Sthat the field laminations or elements21 ofthe motor are bolted to a backing plate 28 which: in turn; is,secured to the extension of the torsion; shaft 8; by means of the key29. The inertia of this combination of field member 21 and backingmember; 28 are. in effect secured to one end oftorsion shaftB and thecomb-tube assen' bly is secured to the other end of torsion shaft 8,Therefore when current is supplied to the series combinationof armatureand field, there will beaseries of torque impulses generated by themotor" which tend to twist the two ends of torsion shaft 8 in oppositedirections. If the frequency of alternating current supplied to themotor" is chosen at half the frequency of the resonant system composedof the comb-tube assembly secured to one end of a torsion shaft and theinertia of the motor field and backing plate at the other, the "motorwill supply torque pulses to the resonant system at its own naturalfrequency. The resonant system comprises the masses and the-torsionalshaft to which the masses are attached which stores up the potentialenergy accounting for the forces opposing the torque pulse. The comb,tube and motor oscillate as a unit on the shaft bearing when the naturalor resonant frequency of the system is attained.

Insofar as the angular amplitude of vibration of the comb is concerned,this is determined, in the case of the eccentric and clutch arrangementfirst described, by the eccentricity of the eccentric, and in the caseof the electromagnetic drive just described, by the magnitude of thecurrent supplied to the coils and armature of the driving system.

Having now described my invention, I claim:

1. A drive for a doifer comb of the type described including meansproviding a resonant torsional system having the doffer comb at least aportion of one of the masses thereof, means providing a second massand acoupling means having a spring torsional shaft connecting said two,

masses.

2. Adrive fora dofier comb of the type described comprising a resonanttorsional system having an elongated dofler comb and supportingstructure forming a mass element of the resonant system, a torsionalshaft forming the resonant coupling element for the doffer comb andstructure attached at one end to said structure and means including inpart an element providing a selected mass joined to the other end ofsaid torsional shaft.

3. A drive for a doffer comb of the type described comprising a resonanttorsional system having an elongated doffer comb and supportingstructure comprising an elongated tube for supporting said comb, atorsional shaft mounted coaxially within said tube and attached rigidly.

at one end to said tube, and means having a desired mass attached to theother end of the torsion shaft for establishing resonance to the systemat the desired frequency and with the desired amplitude of oscillation.

4. A drive for a doffer comb of the type de scribed comprising aresonant torsional system having an elongated doffer comb andsupporting,

structure comprising an elongated tube for support-ingsaid comb, atorsional shaft mounted coaxially within said tube and attached rigidlyat One. end to said tube, with the other end free of the torsionalshaft, and means having a desired mass attached to the other end of thetorsion shaft for establishing resonance to the system at the desiredfrequency and with thedesired amplitudeof oscillation.

, 5. A drive for a dofier comb of the type described comprising a.resonant torsional system having an elongated dofier comb and support-'ing structure forming a mass element of the resonant system, a torsionalshaft forming the resonant coupling element for the doffer comb andstructure attached at one end to said structure, means including in Partan element providing a selectedmass joined to the other end of saidtorsional shaft, and a slipping clutch means rigidly coupled to one endof the torsional shaft.

6. A drive for a dofier comb of the type described comprising a resonanttorsional system having an elongated doffer comb and supportingstructure forming a mass element of the resonant system, a torsionalshaft forming the resonant coupling element for the doifer comb andstructure attached at one end to said structure, means including in partan element providing a selected mass joined to the other end of saidtorsional shaft and a slipping clutch means rigidly coupled to the endof the torsional shaft attached to said structure, and a slipping clutchmeans rigidly coupled to one end of the torsional shaft.

7. A drive for a doifer comb of the type described comprising a resonanttorsional system having an elongated dofier comb and supportingstructure forming a mass element of the resonant system, a torsionalshaft forming the resonant coupling element for the doifer comb andstructure attached at one end to said structure, means including in partan element providing a selected mass joined to the other end of saidtorsional shaft and means for applying torsional motion between saidother end of the torsional shaft and said structure.

8. A drive for a dofier comb of the type described comprising a resonanttorsional system having an elongated doifer comb and supportingstructure comprising an elongated tube for supporting said comb, atorsional shaft mounted coaxially within said tube and attached rigidlyat one end to said tube with the other end free of said torsional shaft,and means for providing torsional motion between the free ends of thetube and shaft including means providing a mass element for establishingdesired resonance attached to said torsional shaft.

9. A drive for a dofi'er comb of the type described comprising aresonant torsional system having an elongated dofier comb and supportingstructure comprising an elongated tube for supporting said comb, atorsional shaft mounted coaxially within said tube having enlarged endsone of which is attached rigidly to said tube and the other serving as afree bearing for the tube and means adapted to apply torsional motion atthe end of the tube to which the shaft is attached rigidly.

10. A drive for a doffer comb of the type described comprising aresonant torsional system having an elongated doifer comb and supportingstructure comprising an elongated tube for supporting said comb, atorsional shaft mounted coaxially within said tube having enlarged endsone of which is attached rigidly to said tube and the other serving as afree bearing for the tube and means adapted to apply torsional motion toone end of said torsional shaft.

11. A drive for a dofier comb of the type de-' scribed comprising aresonant torsional system having an elongated dofier comb and supportingstructure forming a mass element of the resonant system, a torsionalshaft forming the resonant coupling element for the doffer comb andstructure attached at one end to said structure, means including in partan element providing a selected mass joined to the other end of saidtorsional shaft, and a slipping clutch means rigidly coupled to one endof the torsional shaft having a fluid chamber formed in an annularsector coaxially with the torsional shaft in one portion of the clutchwith a close fitting projection having an opening there-throughextending from the facing of the other portion of the clutch wherebyfluid may be forced from one portion of the chamber to the other throughsaid opening controlling the amount of slipping.

12. A drive for a doffer comb of the type described comprising aresonant torsional system having an elongated dofizer comb andsupporting structure comprising an elongated tube for supporting saidcomb, a torsional shaft mounted coaxially within said tube and attachedrigidly at one end to said tube with the other end free of saidtorsional shaft, and means for providing torsional motion between thefree ends of the tube and shaft including a field element of a motorattached to one of the free elements and an armature element attached tothe other free element, both adapted to be energized by alternatingcurrent.

EDWARD W. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,645,794 Bumstead et al Oct. 18,1927 1,961,679 Walti June 5, 1934 1,965,742 Junkers July 10. 1934FOREIGN PATENTS Number Country Date 2,758 Great Britain of 1861 540,453Great Britain Oct. 17, 1941

